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Bye E1,2, Harvey L1, Glinsky J1, Bolsterlee B3,4, Herbert R3,4
1John Walsh Centre for Rehabilitation Research, Sydney Medical School/Northern, University of Sydney, Sydney, Australia, 2Spinal Injury Unit, Prince of Wales Hospital, Sydney, Australia, 3Neuroscience Research Australia (NeuRA), Sydney, Australia, 4University of New South Wales, Sydney, Australia
Background: Partial paralysis is prevalent following spinal cord injury (SCI). It is caused by disruption to some but not all of the motor pathways to a muscle and can have significant implications for motor function. Previous studies have shown that strength training can increase the strength of partially-paralysed muscles but the mechanisms responsible for these strength gains are not known. In able-bodied individuals (people without paralysis) strength gains are thought to be both centrally mediated (improved neural drive) and peripherally mediated (changes in muscle architecture). We have developed new methods for measuring muscle architecture using magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI).
Purpose: To investigate whether strength training changes the architecture of partially-paralysed muscles of people with SCI.
Methods: A pretest-posttest study was conducted in the community. Ten community-dwelling individuals with SCI participated in a six-week strength-training program. One of the following muscle groups was selected as the target muscle for each participant: elbow flexors, elbow extensors, knee flexors or knee extensors. The muscle chosen had to be partially paralysed with grade 1 to 4 strength on the 6-point manual muscle test. Participants were assessed at baseline and after six weeks of training. The outcome of primary interest was physiological cross sectional area (PCSA) measured using MRI and DTI. Other outcomes were mean muscle fascicle length, muscle volume, pennation angle, isometric strength (measured with an isokinetic dynamometer) and muscle grade on a 13-point scale.
Results: On average, training increased muscle volume by 1% (95% CI, -5% to 6%), PCSA decreased by 5% (95% CI, -16% to 6%), mean fascicle length increased by 8% (95% CI, -7% to 24%) and mean pennation did not change (mean 0%; 95% CI, -12 to 13). None of these effects were statistically significant (p > 0.05). Maximal isometric muscle strength increased, on average, by 14% (95% CI, -3% to 30%). The mean change in strength measured on the 13-point manual muscle test scale was 1.5 points (95% CI, 0.5 to 2.5).
Conclusion(s): We did not find any evidence that six weeks of strength training changed muscle architecture in the partially-paralysed muscles. Strength gains produced by six weeks of strength training are likely the result of improved neural drive to muscles or increases in specific muscle tension, but not of changes in muscle architecture.
Implications: Further research is needed to better understand the mechanisms responsible for strength gains in partially-paralysed muscles in people with SCI.
Keywords: Strength training, spinal cord injury, muscle architecture
Funding acknowledgements: The National Health and Medical Research Council and iCARE.
Purpose: To investigate whether strength training changes the architecture of partially-paralysed muscles of people with SCI.
Methods: A pretest-posttest study was conducted in the community. Ten community-dwelling individuals with SCI participated in a six-week strength-training program. One of the following muscle groups was selected as the target muscle for each participant: elbow flexors, elbow extensors, knee flexors or knee extensors. The muscle chosen had to be partially paralysed with grade 1 to 4 strength on the 6-point manual muscle test. Participants were assessed at baseline and after six weeks of training. The outcome of primary interest was physiological cross sectional area (PCSA) measured using MRI and DTI. Other outcomes were mean muscle fascicle length, muscle volume, pennation angle, isometric strength (measured with an isokinetic dynamometer) and muscle grade on a 13-point scale.
Results: On average, training increased muscle volume by 1% (95% CI, -5% to 6%), PCSA decreased by 5% (95% CI, -16% to 6%), mean fascicle length increased by 8% (95% CI, -7% to 24%) and mean pennation did not change (mean 0%; 95% CI, -12 to 13). None of these effects were statistically significant (p > 0.05). Maximal isometric muscle strength increased, on average, by 14% (95% CI, -3% to 30%). The mean change in strength measured on the 13-point manual muscle test scale was 1.5 points (95% CI, 0.5 to 2.5).
Conclusion(s): We did not find any evidence that six weeks of strength training changed muscle architecture in the partially-paralysed muscles. Strength gains produced by six weeks of strength training are likely the result of improved neural drive to muscles or increases in specific muscle tension, but not of changes in muscle architecture.
Implications: Further research is needed to better understand the mechanisms responsible for strength gains in partially-paralysed muscles in people with SCI.
Keywords: Strength training, spinal cord injury, muscle architecture
Funding acknowledgements: The National Health and Medical Research Council and iCARE.
Topic: Neurology
Ethics approval required: Yes
Institution: Neuroscience Research Australia
Ethics committee: University of New South Wales
Ethics number: HC17635
All authors, affiliations and abstracts have been published as submitted.
